poj1655
建树dfs
View Code
#include
<
iostream
>
#include
<
cstdio
>
#include
<
cstdlib
>
#include
<
cstring
>
using
namespace
std;
#define
maxn 20005
struct
Edge
{
int
v, next;
} edge[maxn
*
2
];
int
n, ecount;
int
head[maxn];
int
f[maxn];
int
ans, ansi;
bool
vis[maxn];
void
addedge(
int
a,
int
b)
{
edge[ecount].v
=
b;
edge[ecount].next
=
head[a];
head[a]
=
ecount;
ecount
++
;
}
void
input()
{
memset(head,
-
1
,
sizeof
(head));
ecount
=
0
;
scanf(
"
%d
"
,
&
n);
for
(
int
i
=
0
; i
<
n
-
1
; i
++
)
{
int
a, b;
scanf(
"
%d%d
"
,
&
a,
&
b);
a
--
;
b
--
;
addedge(a, b);
addedge(b, a);
}
}
void
dfs(
int
a)
{
f[a]
=
1
;
vis[a]
=
true
;
int
x
=
0
;
for
(
int
i
=
head[a]; i
!=
-
1
; i
=
edge[i].next)
if
(
!
vis[edge[i].v])
{
dfs(edge[i].v);
f[a]
+=
f[edge[i].v];
x
=
max(x, f[edge[i].v]);
}
x
=
max(x, n
-
f[a]);
if
(x
<
ans)
{
ans
=
x;
ansi
=
a;
}
}
int
main()
{
//
freopen("t.txt", "r", stdin);
int
t;
scanf(
"
%d
"
,
&
t);
while
(t
--
)
{
input();
ans
=
0x3f3f3f3f
;
memset(vis,
0
,
sizeof
(vis));
dfs(
0
);
printf(
"
%d %d\n
"
, ansi
+
1
, ans);
}
return
0
;
}